The present invention relates to plastic containers especially for retention of fluids under pressure, as for carbonated beverages or the like, and to the manufacture thereof. These containers are usually prepared from a preform which may be injection or extrusion molded, followed by blow molding the preform into a suitably shaped container using a blow mold having the desired shape. Typical thermoplastic materials are polyethylene terephthalate (PET), polyolefins, etc., although others can be used.
The container configuration generally includes a neck portion with a cap retaining means, a shoulder portion depending therefrom, a side wall or main body portion depending from the shoulder portion and a bottom portion joined to the side wall and depending therefrom.
For the convenience and economy they represent, the public calls for large size containers, as for example, the two liter PET bottles widely used for carbonated beverages and one gallon milk bottles. Indeed, even larger containers would be desirable. However, these containers are awkward, especially for small children unless provided with means to handle them conveniently.
Accordingly, handles or handgrips are used, made in various ways, depending primarily on the material of the bottle and the process best suited to convert it into the desired shape. In polyethylene (PE) bottles made by extrusion blow molding, a hollow handle may be made by action of the same mold that shapes the extruded preform into the bottle itself, as is well known. The prerequisites for this technique are an extruded preform and a plastic, such as PE, that may be readily pressure welded. Bottles made of PET from injection molded preforms do not have hollow, integral handles, because it is well-nigh impossible to weld PET into a closed handle by the above technique.
The art shows ways to provide handles for PET bottles, but none of them are integral with the body of the bottle, i.e., made from the preform used to blow the bottle itself. Instead, separately made handles are mechanically attached, or molded onto the finished body in a separate molding step, e.g., as shown in U.S. Pat. No. 4,727,997 to Y. Nakamura. This is an expensive and often unreliable procedure that is commercially unsuccessful.
A handgrip may be used as a substitute for a handle, the difference between the two being that, in grasping a handle, at least one finger of the user's hand is inserted into a hole formed by a loop attached to the bottle, or integral therewith while the handgrip, or simply grip, is formed by indentations in the bottle wall designed to permit grasping the grip between the thumb and forefingers.
Such a grip may be readily produced as an integral part of the bottle from an otherwise normal preform in a mold that has a corresponding cavity as part of the one forming the rest of the bottle wall. PET bottles with such a grip are used commercially, as for example to package spirits, wine and other liquids in large sizes, usually over 2 liters.
The same design cannot be used for bottles subjected to internal pressure, as in the case of carbonated beverages, because in a thin-walled, elastic, cylindrical, hollow body subject to internal pressure any shape, including an indentation will assume that of a sphere or cylinder, i.e., evert, obliterating said indentations or other deviation from a substantially circular cross-section.
The purpose of this invention is to provide an economical and aesthetically pleasing bottle made of PET, or other plastics exhibiting comparable molding characteristics, such as polycarbonate, polystyrene, etc., which bottle has a grip as part of its side-wall that will evert in a predetermined fashion under internal pressure and thereby provide its usefulness.
In the past, it was attempted to accomplish this purpose by rendering the wall rigid at the indentations, by providing rib-like reinforcements. U.S. Pat. No. 4,890,752 to A. Ota et al. may serve as an example. The disadvantage is due mostly to excessive wall thickness and corresponding materials' cost of the design if it is to preclude eversion into a shape that is hard to grasp in the hand, particularly at pressures typical of bottled soft-drinks and carbonated water.
Accordingly, it is a principal object of the present invention to provide a blow molded plastic container for carbonated beverages having an improved configuration.
It is a still further object of the present invention to provide a container as aforesaid including a strengthened handgrip portion.
It is a still further object of the present invention to provide a container as aforesaid wherein the strengthened handgrip portion retains its efficacy when the container is filled with a carbonated beverage.
Further objects and advantages of the present invention will appear hereinbelow.